Strange IP address assigned by SAIX

Is it normal for Telkom to assign an IP address that end in .255? I thought that was a broadcast address?

14th of December, 2005
07:05:05 PM 165.xxx.221.255 Login successful.

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yea its normal. broadcast address is when all four are set to 255

w1z4rd said:

Is it normal for Telkom to assign an IP address that end in .255? I thought that was a broadcast address?

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It's been a while but if I remember correctly it has to do with subnet masks. If I have a subnet of 255.255.255.0 then the a IP ending in 255 would be a broadcast address. If my subnet was 255.255.0.0 then I would need both the last two addresses to end in 255 to have an broadcast address.

Cheers

Dean

u can use a broacast address as an ip addres, but this violates the set rules by iee, Telkom shouldnt be issueing thses addresses

Depending on your subnet mask, you can even end up with an address ending in .0 - you can imagine how much Windows likes that!

We have a large subnet assigned via DHCP here at work - we've had to reserve the .0 and .255 addresses, because they cause endless hassles with certain software.

sburrell said:

u can use a broacast address as an ip addres, but this violates the set rules by iee, Telkom shouldnt be issueing thses addresses

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No, it violates the IP (Internet Protocol) rules. If something is transmitted on the broadcast address of a subnet, every machine is supposed to handle it. So if you ping the broadcast address, every machine should respond, though they don't always. Setting your IP as the broadcast address, is a VERY bad idea. I don't think most OS's will even allow it.

The first address in your subnet is always the network address, and the last is your broadcast. .255 has nothing to do with that. Have a look at http://jodies.de/ipcalc

As an example, you can set your subnet mask to 255.255.255.248 (a CIDR range - Classless Inter-Domain Routing, probably what IS use for uncapped DSL), then you will have the following:

Network addy: 192.168.0.0
Broadcast: 192.168.0.7
Usable IPs: 192.168.0.1 - 192.168.0.6 (6 hosts)

The next subnet will be:

Network addy: 192.168.0.8
Broadcast: 192.168.0.15
Usable IPs: 192.168.0.9 - 192.168.0.14 (6 hosts)

And so on.

ISP's use this to give you smaller netblocks, to more efficiently use the available IPv4 addresses. If you have a Class C network address (255.255.255.0), then it will be as follows:

Network addy: 192.168.0.0
Broadcast: 192.168.0.255

If your netmask is 255.255.0.0 (Class B) you have:

Network addy: 10.0.0.0
Broadcast: 10.0.255.255
Usable IPs: 10.0.0.1 - 10.0.255.254 (65534 usable IPs)

Similarly, a Class A (255.0.0.0) will be

Network addy: 10.0.0.0
Broadcast: 10.255.255.255
Usable IPs: 10.0.0.1 - 10.255.255.254 (16777214 usable IPs)

If allowed by whoever assigned the blocks, you can use the following (excluding network and broadcast addresses)

255.0.0.0 - 16777214 hosts
255.255.0.0 - 65534 hosts
255.255.255.0 - 254 hosts
255.255.255.128 - 127 hosts
255.255.255.192 - 62 hosts
255.255.255.224 - 30 hosts
255.255.255.240 - 14 hosts
255.255.255.248 - 6 hosts
255.255.255.252 - 2 hosts
255.255.255.254 - 0 hosts (gives you only broadcast and network addresses)
255.255.255.255 - refers to a single host on the internet

You can split up the addresses larger than Class C as well.

Thanks Valerion .. now even I understand it

Imagine how it bothers bill gates that Apple has a class A address (16 million IP's) and Microsoft only has a class B address (65 000 IP's)

Carlhead said:

Imagine how it bothers bill gates that Apple has a class A address (16 million IP's) and Microsoft only has a class B address (65 000 IP's)

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HP also have one. Must really p|ss him off. HP got is with (Compaq got it with Digital). A few of the founding guys got them.

Cheers

Dean

Not strange at all with a subnet mask of 255.255.0.0...